This hangar type building that has served as a shipyard building in Tersane-i Amire in Haliç, Istanbul which is the oldest operational shipyard in the world, dating back to the Byzantine Empire. The original structure consists of three 18mx125m hangars next to each other. There are alternating masonry walls of approximately 1m width separating these hangars and steel roof trusses on these walls. New traditional arts and handcrafts museum structure designed by Han Tümertekin and commissioned by the Vehbi Koç Foundation has been studied within the original structure. The walls of this existing building are supported by the contemporary building elements, creating new usage areas, and ensuring the seismic and load safety of the original building. The museum structure, which has a total usable area of approximately 25000 m2 museum space plus auditorium additions, are being solved with vertical steel carriers and composite flooring system. At the roof level, the original roof trusses are preserved and the design process continues with alternatives to reinforce the existing or add new steel/wood trusses. Among the many alternatives studied, base isolation units inserted under the existing walls were a unique engineering challenge. This was thought to minimize the operational downtime and insurance and artwork table isolation costs for this very specific building.